1. Field of the Invention
The present invention relates to an optical distance measuring sensor that detects the presence of an object in a prescribed range and a direction in which the object is located and measures a distance to the object. The present invention also relates to a self-propelled cleaner incorporating such a sensor.
2. Description of the Related Art
Conventionally, pyroelectric sensors, ultrasonic sensors, reflection type infrared sensors, infrared distance measuring sensors and so on have been used as sensors intended to detect human bodies and objects, and combinations of some of those different sensors are also used.
As a sensor of the kind, a sensor device including a pyroelectric sensor and an infrared sensor has been proposed. The sensor device detects a human body by the pyroelectric sensor, and then, by the infrared sensor, detects a direction in which the human body is located and measures a distance to the human body (refer to, for example, JP 2002-350555 A). In this sensor device, because the infrared sensor has a detection range narrower than that of the pyroelectric sensor, it has been proposed to detect the direction and the distance of the human body by making the infrared sensor mechanically scan the detection range. Moreover, it has been proposed to use a plurality of infrared sensors in order to cover a detection range roughly equal to the detection range of the pyroelectric sensor.
However, making the infrared sensor mechanically scan the range raises a problem that noises are generated by the mechanical scanning movement and a problem that the responsiveness is comparatively low because of the mechanical scan. This arrangement has a further problem that long-term stability of the sensor device is comparatively poor because of the required maintenance of the scan mechanism.
Using a plurality of infrared sensors has a problem that the sensor device has an increased size, so that apparatuses to be equipped with the sensor device are limited. This arrangement has a further problem that the manufacturing cost is increased due to an increase in parts count. Also, there may occur stray light and difficulties in emitting parallel light depending on the mounting state of the plurality of infrared sensors. These problems cause a disadvantage that the accuracy of the measurement value is lowered. This arrangement also has a problem that every time a light source is switched to another to switch the infrared ray emissions, a period of an irregular output is generated, so that the distance measuring operation takes much time as a whole. Also, there is another problem that the measurement accuracy is prone to be lowered due to susceptibility to the influence of electromagnetic waves.